Facial authentication features on Android devices are often not as secure as Face ID on Apple’s iPhone X, and the same rings true with the Huawei
Nova 4. You cannot use Face Unlock to access secure services like banking apps — it’s purely a convenient way to quickly unlock your phone from the lock screen. If you didn’t configure Face Unlock when you first set up your device, simply go to

Settings > Security & privacy > Face Unlock.

You either need to enter your existing PIN or set one up to use Face Unlock. You then see the Enroll face screen that provides details about the functionality. Tap Continue > Allow. You will see around viewfinder screen appear.

https://newsdailytech.com/how-to-set-up-face-unlock-in-huawei-nova-4/